where \(\Omega _{\rm CDM}\)  is the current energy density of cold dark matter normalized by the total energy density and \(T_{\rm PBH}\)  is the temperature at the PBHs production.
Regions of \(f_{\rm PBH}>10^{-2}\)  are already in the reach of current observations at Subaru HSC [1]} and OGLE [2]}.
On the other hand, future microlensing experiments, such as Roman Space Telescope, can test the parameter region with the fraction \(f_{\rm PBH}>10^{-4}\)  [3]} .
